1. Field of the Invention
The invention relates generally to sealing systems and, more particularly, to non-contacting types of sealing systems for preventing the flow of a fluid through a passageway provided in a wall around a rotating shaft such as an impeller drive shaft for a pump.
2. Prior Art
Several techniques for preventing the flow of fluids through shaft passageways are known. One such system utilizes a closely fitted sealed bearing filled with sealing material for sealing the shaft passageway. Another such system utilizes a dynamic seal commonly known as a slinger seal including a rotating slinger for centrifugally repelling fluids, particularly liquids, away from the shaft.
Although these techniques do prevent the flow of fluids through shaft passageways, sealed bearings are expensive and difficult to manufacture; and slinger-type seals tend to create turbulence in the fluid in which they are immersed. In many applications, where the fluid is a volatile or chemically active liquid, turbulence cannot be tolerated because the foaming caused by the turbulence tends to evaporate or to change the chemical composition of the liquid. An example of such a fluid is the liquid developer used in photocopying machines that must be pumped from a developer tank to a developing station without excessive turbulence to avoid adversely affecting the developing characteristics of the developer.